Method of and apparatus for imparting twist to yarns

ABSTRACT

An apparatus for producing a plurality of pairs of matched yarns having identical twist characteristics in which yarns pass through a processing unit having heaters and twist heads. A composite twist head may be used which has a plurality of annular twisting components driven at the same speed from a common drive source. Alternatively, the twist head may have a single twisting component. The or each component receives one or more pairs of yarns, with the yarns in each pair travelling in respectively opposite directions through the component.

United States Patent Colton 1 Sept. 18, 1973 METHOD OF AND APPARATUS FORIMPARTING TWIST TO YARNS inventor:

Filed:

Lewis Henry Colton, 470 Mansfield Rd., Nottingham, England June 1, 1971App]. No.: 148,837

US. Cl. 57/34 HS, 57/77.45, 57/157 TS Int. Cl. n01 1 /2s,po2 1/04 Fieldof Search ..57/77.3, 57/1, 77.45, 34 R,

57/34 HS, 157 TS, 157 MS References Cited UNITED STATES PATENTS 6/196911/1970 10/1971 1l/l97l MacKintosh 57/77.45 X MacKintosh.... 57/77.4

Peel 66/125 A Wyatt 66/125 A X MacKintosh 57/77.45 X

3,066,473 12/1962 Maeda ..57/77.4

Primary Examiner-Donald E. Watkins Attorney-Holman & Stern [57] ABSTRACTAn apparatus for producing a plurality of pairs of matched yarns havingidentical twist characteristics in which yarns pass through a processingunit having heaters and twist heads.

A composite twist head may be used which has a plurality of annulartwisting components driven at the same speed from a common drive source.Alternatively, the twist head may have a single twisting component. Theor each component receives one or more pairs of yarns, with the yarns ineach pair travelling in respectively opposite directions through thecomponent.

7 Claims, 6 Drawing Figures Patented Sept. 18, 1973 3,759,024

5 Sheets-Sheet 1 TZY'N Patented Sept. 18, 1973 I 3,759,024

5 Sheets-Sheet 3 Patented Sept. 18, 1973 5 Sheets-Sheet 4.

Patented Sept. 18, 1973 3,759,024,

5 Sheets-Sheet 5 "FIG. 6

METHOD OF AND APPARATUS FOR IMPARTING TWIST TO YARNS BACKGROUND OF THEINVENTION This invention relates to the twisting of yarns.

Primarily, although not exclusively, it is concerned with the falsetwisting of continuous, multi-filament, thermoplastic yarns.

PRIOR ART In conventional false twisting apparatus, synthetic yarn istwisted to the extent ofa relatively large number of turns per inch andis heat set. By a relatively large number of turns is, for example,meant any appropriate number in the range from 80 120 per inch; thus ayarn of, say 20 'deniers would have imparted thereto about I turns perinch. In any event, the twisting and heat setting of the yarn results inits bulking up and becoming lively upon subsequent recovery. A falsetwisted yarn is accordingly a stretch yarn suitable for the productionof stretchable fabrics and hosiery, e.g. stockings and tights.

One conventional method of imparting twist to yarn employs a twist headcomprising a driven, rotary, annular component with the yarn beingcaused to roll over the inner surface of the component so that it isfrictionally twisted about its longitudinal axis. The component may, forexample, have trumpet-shaped ends to allow two yarns to besimultaneously passed therethrough in opposite directions. In this way,the two yarns are simultaneously twisted so that respectively oppositehanded twist is imported thereto, i.e. receive an S" and "2 twist.

A conventional yarn processing apparatus employs a plurality of thesetwist heads arranged at spaced positions along a yarn path with heatersinterposed therebetween so that the yarn travels successively throughthe heads and over the heaters. However, even where the heads havetrumpet-shaped ends as mentioned above, hitherto a maximum of two yarnsonly can be simultaneously processed. This is manifestly a severelimitation on the productivity of the apparatus.

An apparatus of this kind may be used to process yarns in the course oftheir delivery to a knitting or other textile machine. In this event,the limitation to a maximum of twoyams restricts the range ofapplication of the apparatus to twin feed machines only. To cater formachines having a greater number offeeds, it has been necessary toprovide additional sets of apparatus, each comprising a set of twistheads and associated heaters. For example, the apparatus must beduplicated for a four feed machine.

Apart from increasing the cost, duplication of the apparatus has thedisadvantage that the yarns may not all be processed under the samecondition in all the sets of apparatus, with the result that theyexhibit different characteristics so that the fabric knitted by themachine is not uniform.

OBJECTS AND SUMMARY OF THE INVENTION yarns, comprising a plurality oftwist heads through a which the yarn pairs successively pass intravelling therethrough, and heaters along which the twisted yarns areheated, with each twist head having one or more rotary annularcomponents through which the pairs of yarns are passed so as to betwisted by frictional contact with their inner surfaces, the yarns inthe or each pair travelling in opposite directions through the samecomponent so that respectively opposite handed twist is impartedthereto.

As will be appreciated, the invention will greatly increase theproductivity of a yarn twisting apparatus without substantiallyincreasing its initial cost. The advantages derived from the inventionwill be particularly significant in a yarn processing apparatusassociated with a knitting machine. In this case, a single set of twistheads can be provided to produce a plurality of pairs of identicallymatched yarns, thereby ensuring uniformity in the knitted fabricproduced from the yarns.

According to one embodiment of the invention, a plurality of pairs ofyarns may be passed through the or each rotary twisting component ofeach twist head in the apparatus, and yarn guiding means are provided inassociation with the head to maintain the yarns at an angular spacingfrom one another, both on entering and on leaving the component.

In another embodiment, each twist head may comprise a plurality ofrotary annular components, through each of which can be passed pairs ofyarns travelling in opposite directions, and means to enable thecomponents to be rotated at the same speeds from a common drive sourceso as to twist the pairs of yarns under the same conditions.

In this latter situation, it is possible to incorporate the common drivesource for the rotary twisting components in the twist head itself. Forexample, an electric or fluid motor could be used with appropriatetransmission means (e.g. gearing) between the motor and the components.Preferably however, belt drive means are employed.

Thus, each rotary component in the head preferably carries a coaxialpulley by which it can be driven in rotation, and all the pulleys in thehead are identical so that the components can be driven at the samespeed from a common drive source.

These pulleys are belt driven from a main driving pulley or pulleysexternally of the head. Normally, the driving pulley(s) will beincorporated in yarn processing apparatus to which the head is fitted,with the belts driving the twisting components being connected after thehead has been fitted to the unit.

The drive from the driving pulley(s) may be direct or via anintermediate shaft. In this case, the twisting components are mountedfor rotation about a common axis and the intermediate shaft is mountedwith its axis parallel to said common axis, and this shaft is adapted tobe driven from an external drive source and carries a plurality ofidentical pulleys, each of which is associ ated with one of thecomponent-driving pulleys and is arranged to drive its associatd pulleythrough a belt.

Preferably, each rotary twisting component has a relatively smallcentral opening which extends axially of the component and merges intotrumpet-shaped ends thereof, each said end having an outwardly flaredconvex surface of annular form and being provided with an initiallyseparate ring which is set in an annular groove in said surface, israised slightly from the general curve of the latter, and is of afriction-engendering material so that yarns travelling through the headare engaged and twisted primarily by contact with said rings;

The invention has been found most useful in connection with theproduction of stockings, pantyhose (sometimes called tights) and similargarments in which it is important for the yarns from which the garmentis knitted to be perfectly matched to ensure uniformity in the finishedgarment. The invention therefore includes within its scope a garment ofthis kind produced by the invention.

To facilitate understanding of theinvention, and to enable it to bereadily carried into practice, reference will now be made to theaccompanying drawings which illustrate two embodiments thereof, by wayof example, and in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a yarnprocessing unit constructed according to the invention, which isassociated with a knitting machine,

FIG. 2 is a vertical sectional view through a twist head of the formemployed in the processing unit of FIG. 1,

FIG. 3 is a diagrammatic perspective illustration, showing the pathsfollowed by the yarns in the unit of FIG. 1,

FIG. 4 is a view of part of a processing unit of the kind shown in FIG.1, to illustrate a different embodiment of the invention,

FIG. 5 is a somewhat diagrammatic view in the direction of arrow A inFIG. 4, with the twist head shown partly in section and its casingindicated in chain lines for clarity, and

FIG. 6 is a diagrammatic side view of a twist head/- heater assemblyaccording to a further aspect of the invention. Like references denotelike parts throughout the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS Referring first to FIG. 1, thedrawings show a processing unit P carried by a vertical shaft S whichprojects upwardly from a four-feed circular knitting machine K ofconventional form. Shaft S also carries a number of bobbins B ofcontinuous, multi-filament, thermoplastic yarns to be delivered to themachine K. Thus, the yarns travel upwards from the bobbins B to the unitP in which they are processed before being delivered to the machine Kfor knitting.

Unit P comprises a frame. (for the sake of clarity indicated as atriangular base :1) which carries a plurality of twist heads T, acompensator C and heaters H. Three of the twist heads, T1, T2 and T3 arepositioned one at each comer of base 1 with the heaters on the slopingsides of the base. On the horizontal side of the base is the remainingtwist head. T4, arranged adjacent twist head T3, and the compensator Cadjacent twist head T1. i

Each twist head T isdriven by a belt system from a flexible drive shaft2, and the shaft 2 is driven from the main drive shaft; of the machineK. The speed of the shaft 2 is correlated with that of the machine by apair Shaft 2 is connected inunit P to a pair of toothed pul leys 6 (oneof which is visible) arranged side by' side andmounted on the frame ofthe unit. One of the pulleys 6 drives a main toothed belt 7 whichfollows a generally triangular path around the frame 1 and is guided byfurther multiple toothed pulleys 8a, 8b, 8c and 8d and by a singlejockey pulley 9.

Oneof the pulley wheels on each of the multiple pulleys 8a to 8d guidesthe main belt 7, while the'other is employed to drive the component ofthe apparatus associated therewith (i.e. a twist head T or, in the caseof pulley 8d, the compensator C) through an auxiliary belt 10.

Before referring to FIG. 2 to explain the construction of the twistheads T, brief reference will be made to the compensator C. It comprisesa casing 11 which is mounted on the frame 6 of the unit and carries apair of horizontal parallel shafts 12 which project from opposite sidesof the casing 11. The projecting parts of each shaft carry a pair ofpulleys 13 around which the yarns pass on entering or leaving the unit.Thus, the pulleys on the shaft 12 at the right hand side of thecompensator in FIG. I carry the yarns as they enter the unit P, theyarns, as they leave the unit, being passed around the pulleys on theleft hand shaft 12. The speed at which the shafts 12 are driven isselected to impart exactly the required drive speed to the yarns both onentering and on leaving the unit P.

Reference will now be made to FIG. 2 which illustrates one of the twistheads T1 or T2 of FIG. 1. The other two twist heads are basically ofsimilar construction; the differences from the FIG. 2 arrangement willbe referred to later. J

Twist head T comprises a hollow casing 14 which is arranged to bemounted at its lower end on the frame 6 of unit P. This casing defines apair of identicalupstanding housings 15, each of which carries a rotaryannular twisting component 16. Each of the components comprises a pairof co-axially disposed elements 17 arranged in opposed positions andrigidly connected by a bushing 18. Each element 17 is generallytrumpetshaped and carries an inset ring 17a of a frictionengenderingmaterial (e.g. a ceramic) by which yarns travelling through thecomponent are engaged and twisted as the latter rotates.

The bushing 18 carries the inner race of a ball bearing 19, and theouter race thereof is mounted in the casing 14 of the head. Alongsidethe inner race of bearing 19, the bushing 18 carries a toothed wheel 20by which the component 16 is driven in rotation in use. Wheel 20 isitself driven by a belt 21 formed with teeth complementary to those'onthe wheel. It will be appreciated that the component 16 in the housing15 at the right hand side of FIG. 2 is of identical construction tothatwhich has just been described and is driven by a similar toothed belt21. Each of these belts extend around the toothed pulley 22 on a commonshaft 23 mounted parallel to the two components 16 in bearings in FIG.1.

As-will be appreciated from the foregoing description, the twist headshown in FIG. 2 is adapted, in this embodiment, to process two pairs ofyarns, one in each component 16, with the yarns in each pair beingpassed in opposite directions through the relevant component 16 so as tohave a respectively opposite handed twist imparted thereto. Thus, eachof the components produces one S and one 2 twist yarn. It is however,'tobe understood that more than one pair of yarns may be passed througheach component 16 within the scope of the invention as will be explainedlater. In the present embodiment, since both of the components 16 areidentical and since they are driven at identical speeds, the two pairsof yarns processed by the head will be perfectly matched, having beenprocessed under identical conditions.

The twist head T3 at the bottom left hand corner of the processing unitP in FIG. 1 is identical with the head of FIG. 2 except that theintermediate shaft 23 (FIG. 2) in the casing 14 is omitted from thetwist head, and the belts 21 driving the components 16 are drivendirectly from the pulley assembly 8b associated with that head. Thus,this assembly is, in fact, a triple pulley assembly, with one pulleybeing driven by the main belt 7 and the other two pulleys driving thebelts 21 of the twist head. Moreover, each of the belts 21 is twistedbetween the pulley assembly 8b and the driving wheel on the relevantcomponent 16 so that the two components 16 are driven in oppositedirection to the components 16 in the other twist heads. Thisarrangement of driving one twist head in the reverse direction is found,in practice, to produce the most advantageous processing conditions.

The final twist head T4 at the bottom of the frame 6 of the unit isidentical with twist head T3 (i.e. the intermediate shaft 23 of FIG. 2in omitted) except that there is no reversal of the drive; in otherwords, the belts 21 are not twisted between the head and the associatedpulley assembly 8c.

FIG. 3 is a diagrammatic illustration showing the paths of the yarnthrough the twist heads in the unit of FIG. 1. Four yarns arranged intwo pairs Y1 and Y2 enter the unit via the compensator C. From here,each pair travels through relevant rotary components 16 of the twisthead T1 at the bottom right hand corner of the unit, over the right handheater H (the heaters have been omitted from FIG. 3 for clarity) throughthe twist head T2 at the top of the unit, over the other heater I-I,through the twist head T3 at the bottom left hand corner of the unit(driven in opposite direction to the other twist head), through thetwist head T4 at the bottom of the unit and back to the compensator Cbefore being delivered to the machine. As will be appreciated, the yarnsin each pair follow identical paths and are twisted under identicalconditions so that, on leaving the unit, two pairs of perfectly matchedyarns have been produced. This ensures uniformity and evenness in thefabric into which the yarns are knitted.

As will be appreciated, by increasing the number of coaxial rotarycomponents 16 in each twist head and correspondingly increasing thewidth of the heaters, an even greater number of pairs of yarns may beprocessed under identical conditions in accordance with the invention.For example, by doubling the size of each twist head compared with theFIG. 2 arrangement, four pairs of matched yarns may be produced in asingle processing unit.

FIGS. 4 and 5 illustrate a different embodiment of the invention.

FIG. 4 shows part of a yarn processing apparatus similar to that shownin FIG. 1 and comprises a base frame 1 which is of triangular shape andhas a twist head T mounted at each corner thereof. In this embodiment,the twist heads T are similar to those shown in FIGS.

Thus, the yarns Y1, Y2 of one pair enter respectivelyopposite sides ofthe twisting component 16 straight from the heater H. The other pair Y3,Y4 travel parallel to the yarns Y1, Y2 over the heater H but, beforereaching the twist head, are each deflected by a guide G so as to enterthe twist head, at an angular spacing to the corresponding yarn Y1 or Y2in the other pair. Similarly, on leaving the twist head, the yarns Y3,Y4 pass through guides G which deflect the yarns back into the same pathas the yarns Y1. As can be seen from FIG. 5, the guides G are arrangedso that each yarn Y is drawn closely into contact with the inset rings17a and travels in contact with the surface of component 17 on each sideof each of the rings. This ensures that a positive frictional twist isimparted to the yarn.

It will be appreciated that, within the scope of the invention, it wouldbe possible to simultaneously pass more than two pairs of yarns througha single rotary component so long as the yarns are separated byappropriate guides at opposite sides of the component.

Moreover, in a twist head of the form illustrated in FIG. 2 having twoor more rotary annular components, a plurality of pairs of yarns can bepassed through each component, For example, (as indicated at DT in FIG.5) a double twist head can be employed, with a correspondingly widerheater. Each rotary component then receives and twists two pairs ofyarns, thereby enabling four pairs of identically matched yarns to beproduced by the processing unit. Of course, by increasing the number ofpairs of yarns twisted by each component, the scope of the processingunit can be increased even more.

In this way, it is possible to widen the scope of application of theinvention even further. For example, a processing apparatus constructedaccording to the invention may be adapted to feed yarn to a multi-feed(i.e. large diameter) machine (e.g. an interlock or single or doublejerseymachine).

In this event, packages of flat, i.e. unprocessed, yarn carried on acreel may befed to the machine through a processing unit in accordancewith the method of the invention. The large number of yarns required bysuch a machine can be processed using a relatively small number of twistheads by simultaneously passing a large number of pairs of yarns througheach head using guides as shown in principle by FIGS. 4 and 5.

The processing unit may be mounted intermediate the creel and machineand feed yarn to the latter through a distributor head on top of themachine.

A second example of an application of the invention is in thepreparation of warp beams. FIG. 6 illustrates diagrammatically a part ofa processing unit constructed according to the invention for thispurpose.

The drawing shows a twist head T, of similar construction to thatillustrated in FIGS. 4 and 5, arranged with its axis of rotationhorizontal. At each side of the head is a yarn guide 26 comprising ahorizontally directed comb 27 having five teeth 28 on each of which ismounted a tube 29 by which the yarns are guided. Each comb shown has anidentical partner (not visible) with its teeth directed in the oppositedirection.

The pair of combs 28 at the left hand side of FIG. 6 guide to the twisthead, five pairs of flat yarns delivered thereto from a creel (notshown), with the yarns in each pair passing through the head in oppositedirection. The other pair of combs guide the yarns leaving the head overa common heater H having its heating surface disposed in a verticalplane. From here, the yarns may pass through further twist heads andover further heaters according to the desired twist characteristics tobe imparted thereto, before being wound onto the warp beam.

The vertical positioning of the heaters H enables further similar twisthead/heater assemblies to be grouped side by side in a minimum space.Thus, in the case of a warp beam carrying 500 yarns, it would benecessary to provide 50 side-by-side assemblies of the kind shown inFIG. 6 each processing 10 yarns.

Of course, the heater H could, if convenient, be mounted at any otherangle.

In any twisting apparatus of the kind with which the invention isconcerned, it is thought that the yarns must be deflected to a minimumextent while they are actually being twisted, but that there is nolimitation on the amount of deflection which can be employed afterwards.

I claim:

1. Apparatus for producing a plurality of pairs of matched, processedyarns having identical twist characteristics, comprising a plurality oftwist heads through which the yarns pairs successively pass intravelling through the apparatus, and heaters along which the twistedyarns are heated, each twist head comprising a plurality of rotaryannular components, through each of which can be passed pairs of yarnstravelling in opposite directions so that respective opposite handedtwist is imparted thereto by frictional contact with their innersurfaces, and means to enable the components to be rotated at the samespeeds from a common drive source so as to twist the pairs of yarnsunder the same conditions.

2. Apparatus according to claim 1, wherein each rotary component in thehead carries a co-axial pulley by which it can be driven in rotation,all the pulleys in the head being identical so that the components canbe driven at the same speed from a common drive source.

3. Apparatus according to claim 2, wherein the rotary twistingcomponents are mounted for rotation about a common axis, and wherein anintermediate drive shaft is provided in the head with its axis parallelto said common axis, said shaft being adapted to be driven from anexternal drive source and carrying a plurality of identical pulleys,each of which is associated with one of the component-driving pulleysand is arrangedto drive its associated pulley through a belt. .4.Apparatus according to claim 3, wherein the intermediate drive shaftcarries a pulley by which it can be driven from an external drive pulleythrough a belt.

5. Apparatus for producing a plurality of pairs of matched, processedyarns having identical twist characteristics comprising a plurality oftwist heads through which the yarn pairs successively pass in travellingthrough the apparatus, and heaters along which the twisted yarns areheated, each twist head including at least one rotary annular componentthrough which the pairs of yarns are passed so as to be twisted byfrictional contact with their inner surfaces, the yarns in each pairtravelling in opposite directions through the same component so thatrespectively opposite handed twist is imparted thereto, each rotarytwisting component having a relatively small central opening whichextends axially of the component and merges into trumpet-shaped endsthereof, each said end having an outwardly flared convex surface ofannular form and being provided with an initially spearate ring which isset in an annular groove in said surface, is raised slightly from thegeneral curve of the latter, and is of a friction-engendering materialso that yarns travelling through the head are engaged and twistedprimarily by contact with said rings.

6. Apparatus for producing a plurality of pairs of matched, processedyarns having identical twist characteristics, comprising a plurality oftwist heads through which the yarn pairs successively pass in travellingthrough the apparatus, and heaters along which the twisted yarns areheated, each twist head including at least one rotary annular componentthrough which the pairs of yarns are passed so as to be twisted byfrictional contact with their inner surfaces, the yarns in each pairtravelling in oppsoite directions through the same component so thatrespectively opposite handed twist is imparted thereto, said apparatusbeing intimately associated with a knitting or other textile machine andincluding a plurality of pulley assemblies which are associated one witheach twist head and from which the rotary components in the twist headsare driven by belts, said assemblies themselves being driven at a speedcorrelated to that of the machine.

7. Apparatus according to claim 6, wherein a common drive belt drivablyengages each of the pulley assembliesand it itself driven from theknitting or other textile machine by a flexible drive shaft so that thespeed at which the common drive belt is driven and hence the speed ofthe rotary twisting components in the twist heads varies with the speedof the machine.

a t i 8 I

1. Apparatus for producing a plurality of pairs of matched, processedyarns having identical twist characteristics, comprising a plurality oftwist heads through which the yarns pairs successively pass intravelling through the apparatus, and heaters along which the twistedyarns are heated, each twist head comprising a plurality of rotaryannular components, through each of which can be passed pairs of yarnstravelling in opposite directions so that respective opposite handedtwist is imparted thereto by frictional contact with their innersurfaces, and means to enable the components to be rotated at the samespeeds from a common drive source so as to twist the pairs of yarnsunder the same conditions.
 2. Apparatus according to claim 1, whereineach rotary component in the head carries a co-axial pulley by which itcan be driven in rotation, all the pulleys in the head being identicalso that the components can be driven at the same speed from a commondrive source.
 3. Apparatus according to claim 2, wherein the rotarytwisting components are mounted for rotation about a common axis, andwherein an intermediate drive shaft is provided in the head with itsaxis parallel to said common axis, said shaft being adapted to bE drivenfrom an external drive source and carrying a plurality of identicalpulleys, each of which is associated with one of the component-drivingpulleys and is arranged to drive its associated pulley through a belt.4. Apparatus according to claim 3, wherein the intermediate drive shaftcarries a pulley by which it can be driven from an external drive pulleythrough a belt.
 5. Apparatus for producing a plurality of pairs ofmatched, processed yarns having identical twist characteristicscomprising a plurality of twist heads through which the yarn pairssuccessively pass in travelling through the apparatus, and heaters alongwhich the twisted yarns are heated, each twist head including at leastone rotary annular component through which the pairs of yarns are passedso as to be twisted by frictional contact with their inner surfaces, theyarns in each pair travelling in opposite directions through the samecomponent so that respectively opposite handed twist is impartedthereto, each rotary twisting component having a relatively smallcentral opening which extends axially of the component and merges intotrumpet-shaped ends thereof, each said end having an outwardly flaredconvex surface of annular form and being provided with an initiallyspearate ring which is set in an annular groove in said surface, israised slightly from the general curve of the latter, and is of afriction-engendering material so that yarns travelling through the headare engaged and twisted primarily by contact with said rings. 6.Apparatus for producing a plurality of pairs of matched, processed yarnshaving identical twist characteristics, comprising a plurality of twistheads through which the yarn pairs successively pass in travellingthrough the apparatus, and heaters along which the twisted yarns areheated, each twist head including at least one rotary annular componentthrough which the pairs of yarns are passed so as to be twisted byfrictional contact with their inner surfaces, the yarns in each pairtravelling in oppsoite directions through the same component so thatrespectively opposite handed twist is imparted thereto, said apparatusbeing intimately associated with a knitting or other textile machine andincluding a plurality of pulley assemblies which are associated one witheach twist head and from which the rotary components in the twist headsare driven by belts, said assemblies themselves being driven at a speedcorrelated to that of the machine.
 7. Apparatus according to claim 6,wherein a common drive belt drivably engages each of the pulleyassemblies and it itself driven from the knitting or other textilemachine by a flexible drive shaft so that the speed at which the commondrive belt is driven and hence the speed of the rotary twistingcomponents in the twist heads varies with the speed of the machine.